Method of repointing a reflector array antenna

Abstract

The present invention relates to a method of repainting a reflector array antenna comprising a plurality of radiating elements and being of the type that forms beams by computation, in which method each signal received by said antenna is sampled. The method comprises the following operations: estimating the depointing of the radiation pattern of the antenna to obtain a phase shift matrix, computing the discrete inverse Fourier transform of the signal samples supplied by the radiating elements, multiplying the phase shift matrix by the inverse Fourier transform of the sampled signal, and computing the discrete direct Fourier transform of the product of the phase shift matrix and the inverse Fourier transform of the sampled signal.

What is claimed is:  
     
       1. A method of repointing a reflector array antenna comprising a plurality of radiating elements and being of the type that forms beams by computation, in which method each signal received by said antenna is sampled, 
       said method comprising the following operations:  
       estimating the depointing of the radiation pattern of said antenna to obtain a phase shift matrix,  
       computing the discrete inverse Fourier transform of the signal samples supplied by the radiating elements,  
       multiplying said phase shift matrix by said inverse Fourier transform of said sampled signal, and  
       computing the discrete direct Fourier transform of the product of said phase shift matrix and said inverse Fourier transform of said sampled signal.  
     
     
       2. A method according to  claim 1 , wherein said Fourier transforms link the angles of the radiation pattern of said antenna to linear coordinates in the focal plane of said reflector. 
     
     
       3. A method according to  claim 1 , wherein sampling is effected after transposing the frequency of the radio frequency signal down to a frequency in an intermediate frequency band or in baseband. 
     
     
       4. A method according to  claim 1 , wherein, to obtain said phase shift matrix, the depointing is estimated by a first order digital closed loop from the known position of at least one fixed beacon. 
     
     
       5. A method according to  claim 4 , wherein said digital closed loop uses the ratio of the difference of the amplitudes of the signals obtained from two adjacent radiating elements of said antenna to their sum. 
     
     
       6. A method according to  claim 1 , wherein said beams formed by computation are repointed simultaneously. 
     
     
       7. A method of repointing a reflector array antenna comprising a plurality of radiating elements and being of the type that forms beams by computation, in which method each signal ready to be sent by said antenna is also sampled, 
       said method comprising the following operations:  
       estimating the depointing of the radiation pattern of said antenna to obtain a phase shift matrix,  
       computing the discrete direct Fourier transform of the signal samples to be transmitted by the radiating elements at a given time,  
       multiplying said phase shift matrix by said direct Fourier transform of said sampled signal, and  
       computing the discrete inverse Fourier transform of the product of said phase shift matrix and said direct Fourier transform of said sampled signal.